<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div>
        <script>
            var carname1 = "Volvo XC60";
            var carname2 = 'Volvo XC60';
            var answer1 = "It's alright";
            var answer2 = "He is called 'Johnny'";
            var answer3 = 'He is called "Johnny"';
            var answer4 = 'It\'s alright';
            var answer5 = "He is called \"Johnny\"";
            document.write(carname1 + "<br>")
            document.write(carname2 + "<br>")
            document.write(answer1 + "<br>")
            document.write(answer2 + "<br>")
            document.write(answer3 + "<br>")
            document.write(answer4 + "<br>")
            document.write(answer5 + "<br>")
        </script>
        <!-- 字符串添加转义字符来使用引号 -->
    </div>
    <hr />
    <div>
        <script>
            var txt = "Hello World!";
            document.write("<p>" + txt.length + "</p>");
            var txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
            document.write("<p>" + txt.length + "</p>");
        </script>
        <!-- 内置属性 length 来计算字符串的长度 -->
    </div>
</body>

</html>